Is anyone else surprised (and perhaps a little bit alarmed) by the fact that it's September already? This year has been going by exceptionally fast - by rights it should perhaps be mid-May, no later.

Anyone who knows me will know how I do tend to bang on about this - time accelerating as you get old - quite a bit. However, I haven't blogged about it yet so it will be interesting to put my ramblings in some kind of order.

It's a common enough observation - those long hot childhood summers that seemed to last for about five years in today's temporal currency... a two and a half hour car journey being an eternity of boredom at the age of eight... and the past decade passing like a flash. But why does it happen? I've heard a number of theories advanced.

Time is measured as a proportion of your life so far

This sounds plausible. Let's take a week. When you're five years old, a week is 0.38 per cent of your life. When you're thirty five a week is only 0.05 per cent of your life - 0.38 per cent of your life is nearly seven weeks. So if explanation of the phenomena is true, a week as a five year old seems to last as long as seven weeks as a thirty-five year old adult and by extension a thirty-five year old's week is the subjective equivalent of a five year old's day...

This could be true, but it doesn't quite seem as linear as that in real life, so perhaps it's controlled by something not quite as straightforward as how long you've been alive so far.

Subjective time is controlled by the speed of your metabolism

Quite a convincing one, this. If the experience of time is measured by the brain and the brain has a clock-speed which is controlled by the metabolism then as the metabolism slows then time will seem to speed up. The metabolism doesn't necessarily slow at a fixed rate which would explain the non-linearity of the phenomenon as experienced (by me anyway).

It's not who you do, it's what you do...

Some things pass by very quickly whilst others - Friday afternoons at work for instance - drag interminably (on some level I'm sure I'm still at work last Friday). Oddly this fast time (for example 2007 so far) and this slow time (Friday afternoons at work) seem to co-exist. I'm kind of reminded of a Douglas Adams quote:

"Well the hours are good... but now you come to mention it most of the minutes are pretty lousy"

I think a lot of it may have to do with how much you're actually doing and whether you're stuck in a routine or not - keeping busy with varied and constantly fresh activities would seem to me to be the way forward when it comes to slowing time down again.

However, I'm about to start reading Making Time: Why Time Seems to Pass at Different Speeds and How to Control It by Steve Taylor, so maybe that has the answer...